Ozone is a naturally occurring allotrope of oxygen. It has been known and used as an oxidant and disinfectant. In aqueous solutions, ozone is capable of killing bacteria in seconds at appropriate concentrations. It is often desirable to use ozone as a disinfecting or sanitizing agent as it imparts no odor and leaves no residue. The sanitizing properties of ozone dissolved in water, as well as its lack of odor and residue, make such a solution desirable to use for cleaning and disinfecting. Ozonated water can be used to disinfect or sanitize in both commercial and home settings. For example, ozonated water can be used to disinfect or sanitize bathroom counters, produce, dishes and cutlery, or floors.
One convenient method for using ozone as a disinfectant or sanitizes is to dissolve it in water or a water based solution. The stability of ozone is often a complicating factor in its use as a disinfecting or sanitizing agent since the high reactivity of ozone, which imparts its disinfecting and sanitizing properties, also results in reaction with reducing agents and, therefore, decomposition. In light of the poor stability of ozone, however, one difficulty is the delivery of ozonated water in an “on demand” basis. Ozone in ozonated water, produced in anticipation of demand, will eventually decompose and return to being non-ozonated water.
Known ozonation systems for producing ozonated water suitable for cleaning, disinfecting or sanitizing are designed with a tank of water and a recirculating ozonating flow path. The water flows through the ozonating flow path and dissolves an amount of ozone therein. Low efficiency in the ozonating flow path results in the need to recirculate the ozonated water back through the ozonation flow path in order to achieve the desired amount of dissolved ozone. This is typically achieved by recirculating the ozonated water back into the tank of water and running the ozonation system for a period of time until all the water in the tank is sufficiently ozonated.
Known ozonation systems have addressed the delay between (a) starting the system and (b) delivery of ozonated water having a usable level of ozone, by increasing the efficiency of the ozonating flow path and/or by using a continuously recirculating system.
It is possible to produce ozonated water “on demand” using a continuously recirculating system. Continuously recirculating systems have an ozonation flow path that recirculates ozonated water back to the holding tank, and the system ozonates the water in the system regardless of whether ozonated water is being dispensed. In such systems, ozone is continuously added to the water to replace any ozone that has decomposed, or to ozonate any fresh water that has been added to replace ozonated water removed from the system. A steady-state of ozonated water is eventually reached based on the inlet and outlet flow rates, as well as the efficiency of the ozonation flow path. However, at the start of ozonation, the level of dissolved ozone is low and gradually increases until the steady-state is achieved.
There are a number of disadvantages with continuously recirculating systems. For example: they require energy to produce the constantly required ozone; ozone is corrosive with some materials; and there may be a fluctuation in the level of dissolved ozone if a significant amount of ozonated water is removed from the tank.
In traditional ozonation systems, both continuously and non-continuously recirculating systems, there is a delay between the start of the ozonation and the delivery of the ozonated water. A user must wait for the tank of water to be ozonated before the ozonated water can be used. In recirculating systems, starting the ozonation system and removing water from the tank before the ozonation is finished results in non-ozonated water or water with a low level of ozone dissolved therein. In continuously recirculating systems, a user must still wait for the level of ozonation in the water to increase to a usable level. During this time, the continuously recirculating system is either discharging water with low levels of ozone dissolved therein or not discharging water at all.
It is therefore desirable to provide an ozonation system that can dispense ozonated water “on demand” without the need for a continuously recirculating system, (i.e. an ozonation system that dispenses ozone via a single pass through the ozonating flow path) thereby doing away with the need for a holding tank.
Some ozonation systems use devices to separate, for example, water from undissolved ozone gas. Such devices are generally known as “off-gas” units, “degassing” units, or “gas-liquid” separators. All such devices take, as an input stream, a mixture of gas and liquid and provide, as separate output streams, a degassed liquid and a separated gas. The degassed liquid can have gas dissolved therein, even though bubbles of gas have been removed. Depending on the desired outlet stream, a gas-liquid separator can be used to produce, for example, a humidified gas stream, a gas-enriched liquid stream, or a completely degassed liquid.
Under conditions where the flow rate of a liquid is not crucial, the liquid can be degassed simply by letting the liquid and gas naturally separate due to differences in density between the liquid and gas. This process can be accelerated by placing the gas-liquid mixture under an external vacuum. In this situation, the reduced solubility of the gas is caused by the external vacuum, which encourages the gas to separate from the liquid in order to fill the vacuum.
Some known system use centrifugal separation to encourage the separation of gas from a gas-liquid mixture. In such systems, the degassing is achieved by the centrifugal forces on a liquid having a vortex flow. The centrifugal flow of liquid results in pressure differences in the liquid as a function of distance from the center axis of rotation. The low density gas and gas-liquid mixture are collected in the low pressure zone along the center of rotation, while the high density liquid is collected in the high pressure zone around the perimeter of rotation.
Increasing the flow rate in a given size of gas-liquid separator increases the centrifugal force in the vortex flow, resulting in a lower pressure in the low pressure zone and a higher pressure in the high pressure zone. This increase in centrifugal force hastens the separation of gas from the liquid. However, higher flow rates also lead to increased turbulence in the liquid flow as well as a lower residence time in the gas-liquid separator. This increased turbulence and lower residence time discourage separation of gas from liquid and lead to bubbles entering the degassed liquid output stream.